This invention relates to automotive safety glass panels, and particularly to a method for removing the protruding edge area of a plastic sheet in a safety glass panel. The invention is particularly applicable to windows and windshields used in automotive vehicles. The term "windows" is used herein to collectively refer to windshields, side windows and rear windows in automotive vehicles.
In the manufacture of safety glass panels for the windows in automotive vehicles, it is a common practice to provide a sheet of elastomeric-plastic material between two panes of glass. The elastomeric-plastic sheet is bonded to both glass panes, so that in a crash situation the elastomeric-plastic sheet acts as a continuous substrate for restraining the class fragments against high speed separation from the sheet. Typically, the elastomeric-plastic sheet is formed of a stretchable vinyl butyl material.
In the manufacture of a laminated safety glass panel the stretchable elastomeric-plastic sheet is made slightly oversize, relative to the associated glass panes, in order to ensure that each glass pane will have its entire surface bonded to the elastomeric-plastic sheet. The oversize nature of the elastomeric-plastic sheet necessitates that peripheral edge areas of the sheet be trimmed (cut-away) prior to installation of the safety glass window in the vehicle.
In the past, the protruding edge area of the elastomeric-plastic sheet has been trimmed off (cut-away) manually, using a razor blade. Such a procedure is objectionable in that the process is time-consuming. Also, the process can produce stress-riser nicks in the edges of the glass panes. Also, there is some danger that the human technician will be cut at some time during the process.
Recently, there has been introduced a robotic machine for removing the protruding edge area of the plastic sheet by the mechanical slicing action of a razor blade supported on a mechanical arm that is adapted to traverse the edge area of a safety glass panel. The robotic mechanism speeds up the process, and reduces the risk of human injury. However, the razor blades must be replaced frequently, and the edge formed by the razor blade is somewhat jagged.
The present invention relates to a method for removing the protruding edge area of an elastomeric-plastic sheet in a safety glass panel, wherein a rotary grinding wheel is employed as the cutting instrumentality. The grinding wheel has the advantage that a relatively smooth regular edge is formed on the plastic sheet, in a single pass of the cutting machine. Preferably the method is performed with a robotic manipulator that is programmed to produce a relatively constant pressure of the wheel on the edge of the plastic sheet during the entire traverse of the safety glass panel across the grinding wheel.
The wheel is oriented to the panel so that the wheel rotates in a plane transverse to the plane of the safety glass panel, whereby fragments of elastomeric-plastic material are directed away from the panel so as not to clog the pores of the grinding wheel, or otherwise interfere with the grinding operation.
Further features of the invention will be apparent from the attached drawings and description of an apparatus that can be used in practice of the invention.